The present invention relates to the field of thermal energy management, and more particularly to a method and apparatus for dissipating thermal energy produced by removable modules, such as modules used in cable television systems.
There are currently various devices on the market using removable modules that can be inserted into an insertion port for electrical connection with another device. These removable modules may contain a programmable circuit containing, for example, proprietary algorithms for providing information or controlling access to another device. The programmable circuit can include, for example, a Static Random Access Memory (SRAM) or the like to form a confidential or secured portion of the removable module memory in which the proprietary algorithm is stored.
Cable television systems in particular may use removable modules to allow subscribers controlled access to dozens or even hundreds of channels of television programming. The current trend is for cable television systems to provide additional services such as premium channels, pay-per-view programming, video-on-demand programming and even internet access. In advanced cable television systems, each subscriber is typically provided with a set-top terminal. The set-top terminal is a box of electronic equipment that is used to connect the subscriber""s television, or other electronic equipment, to the cable television system. The set-top terminal processes the signal received from the cable television system to provide the services of the cable system to subscribers.
As the premium services of the cable television system expand, security techniques for those premium services become crucial to ensure that only subscribers who have paid for the premium services have access to them. For example, premium channels, such as some movie channels, are scrambled before transmission to prevent unauthorized reception and viewing of those channels. Subscribers who pay additional fees to receive the premium channel or channels are provided with the means to descramble and view the premium channel or channels.
There are many techniques for controlling the remote descrambling of scrambled television signals. Typically, a system subscriber who has paid to receive the scrambled premium channel or channels is provided with a descrambler unit that is connected between the source of the television signal source (e.g., a cable feed or a satellite receiver) and the subscriber""s television set. While this descrambler unit may be a self-contained unit, descrambling circuitry is frequently and preferably incorporated into the subscriber""s set-top terminal.
Unfortunately, proprietary algorithms used by descrambling circuitry can frequently, with enough effort, be xe2x80x9cbrokenxe2x80x9d or duplicated by an unauthorized party. Thereafter, unauthorized means of descrambling the cable system""s premium channels might be made available to subscribers. To avoid this, the operator of the cable system may need to periodically change the proprietary algorithm used to scramble and descramble premium channels.
If the subscriber""s descrambling circuitry is incorporated in a set-top terminal, the old descrambling circuitry must be removed and new descrambling circuitry inserted. To facilitate this process, the descrambling circuitry can be included in the removable modules to plug into a removable module port of the set-top box. The removable modules in this context are also known as point-of-deployment (POD) modules. When the descrambling circuitry is to be changed or upgraded, the old removable module can be pulled from the set-top box, and a module with the new circuitry is inserted in the port. Other elements or programming of the set-top terminal that need to be updated periodically can also be provided in the removable module.
In this application, the removable module is meant to be removed when the cable television company providing the services decides to update or change the proprietary decrypting algorithm or when the cable subscriber changes cable service providers and thus changes decrypting algorithms. Such a change may occur infrequently, in the case when the cable subscriber does switch cable service providers, or regularly as a security precaution, when improved security or other features become available for inclusion in the set-top boxes, or after the decrypting algorithm has been broken by an unauthorized user. Additionally, the inadvertent removal of the removable module typically renders the set-top box non-functional.
Moreover, as noted above, the current trend is for the amount and diversity of services provided by cable television companies to expand to include, for example, the transmission of computer data, a greater quantity of television programming and, eventually, telephone calls. To accommodate the existing and new services, set-top terminals will eventually require many more ports than presently exist. This will reduce the space available for including a separate port for a removable module.
Placing the removable module underneath and, perhaps, inside the casing of the set-top terminal, however, contributes to other problems in the design of the set-top box. Specifically, the electronic circuitry of the removable module inherently generates heat or thermal energy during operation. This thermal energy must be dissipated efficiently to prevent accumulation and overheating that may damage or be detrimental to the module or the device in which the module is inserted. Although prior art devices using PCMCIA cards attempt to dissipate heat away from the card by conducting heat through the card contacts to a main board in the device, this method risks damage to the main board if the amount of heat generated by the card overcomes the main board""s ability to dissipate it. Further, removable modules are being developed that generate more heat than PCMCIA cards, making efficient dissipation of heat even more important. Note that control and dissipation of thermal energy is also important if the removable module is used in applications other than cable television set-top boxes.
Therefore, there is a need in the art for an improved method and apparatus for managing the thermal energy generated by the operation of a removable module when it is inserted into a removable module port.
It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide an improved method and apparatus for managing the thermal energy generated by the operation of a removable module in a set-top box of a cable television system or any other device requiring insertion of a removable module into a removable module port.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
The invention is directed to a guide member, preferably a guide member for receiving a removable module that electrically connects to circuitry when the removable module is inserted into the guide member. In one embodiment, the guide member forms or is otherwise disposed in a removable module port and includes a first surface that is in physical contact with the removable module when the removable module is inserted into the guide member and at least one thermally conductive element on the first surface that provides a physical heat dissipation path from the exterior of the removable module to the exterior of the guide member and into the ambient air. The guide member is made of a thermally conductive material to ensure an efficient transfer of thermal energy away from the removable module.
The guide member may align and guide the removable module into proper connection with a module connector in the removable module port. This facilitates the insertion and connection of the module to the set-top box.
The present invention also comprises the method of implementing the apparatus described above. Specifically, the present invention includes a method of managing thermal energy dissipation in a set-top box for use in a cable television system, where the set-top box has a removable module port formed at least in part by the guide member for receiving a removable module therein. The method is performed by conducting thermal energy away from the removable module to ambient air through at least one surface of the guide member that is in physical contact with the removable module when the removable module is placed in the guide member.